In extremely cold conditions, the two most important requirements for clothing--to provide humans with the ability to survive and/or be comfortable--are the necessity of reducing heat loss from the body, and permitting the controlled transmission of moisture produced by perspiration. Traditionally, the reduction of heat loss has been accomplished by wearing heavy garments and/or by putting on multiple layers of garments. The transmission of moisture has been provided for in various ways, such as by wearing of vapor permeable garments, providing ventilation at the cuffs or collars, deliberately providing vent holes in the garments, etc. Within approximately the last decade and a half, two different systems have emerged for providing enhanced comfort, and/or survivability, even under extremely cold conditions and harsh environments.
One of the two cold weather garment systems that is most accepted is known, for civilian garments, as the Patagonia system, and its closely related military counterpart is the ECWCS system. These are layered systems consisting of three or more separate garments that are worn one over the other, each set consisting of an upper body series of layers, and a lower body series of layers. The outer set in the ECWCS system is of Gore-Tex laminated polytetrafluorethylene fabric.
Another accepted and very successful "cold weather system", which has been proven effective in a wide variety of cold weather climates, is known as the Phillips system, and was developed by the well known outdoorsmen J. G. Phillips, Jr. and Sr. This system comprises unitary garments, rather than layers. The garment is made up of three components an outer or "shell" layer of military nylon camouflage fabric selected for its ruggedness and high permeability to air and moisture vapor; an approximately one inch thick layer of soft and flexible polyurethane open cell foam; and an interior woven or knit lining fabric. The three components are sewn together to form a unitary garment. As a single garment system, rather than a multi-layered system, the Phillips system has a number of advantages over the ECWCS system. However the Phillips system has one significant drawback, and that is low wind resistance. The low wind resistance of the Phillips system limits the versatility of this otherwise very effective system.
Despite the fact that the Phillips system has been known and used commercially for more than a decade and a half, heretofore its low wind resistance problem has not been solved. However, according to the present invention, a cold weather garment, and a method of utilization of the cold weather garments, have been provided which solve the low wind resistance problem of the Phillips system, while retaining all of the other advantages thereof The single-set system of garments (that is an upper body garment including arm portions, and a lower body garment comprising leg portions) has excellent warmth, moisture permeability, wind resistance, and water resistance properties.
The most significant distinction between the invention and the Phillips system is the composition of the outer or shell fabric. The outer fabric of the garment according to the present invention has extremely low air permeability, while still having very high moisture vapor transmission. That is, the air permeability of the outer fabric according to the invention is less than 15 cubic feet per minute per square foot at 0.5 inches head of water, and preferably is less than 10 cubic feet per minute per square foot. Despite this low air permeability, the outer fabric of the garment according to the present invention has a moisture vapor transmission of at least 1,000 grams per square meter per 24 hours.
The preferred outer fabric according to the invention is a woven fabric, constructed from a fine denier, multi-filament, synthetic yarn (preferably polyester yarn) which is woven into a high density construction with controlled air porosity and moisture vapor transport properties. One commercially available fabric that is eminently suitable as the outer fabric according to the invention is sold by Burlington Industries, Inc. of Greensboro, N.C. under the trademark "VERSATECH".
The garments according to the invention comprise, in addition to the outer fabric specified above, an interior lining, which may be the same as for the Phillips system, and preferably comprises a loosely knit nylon or polyester tricot fabric.
Between the inner and outer fabrics is at least a 1/2 inch layer, and preferably about a one inch layer, of open cell polyurethane foam, of the same type as in the Phillips system. Alternatively, the foam can comprise a convoluted foam, which has a number of advantages compared to conventional parallel sided foam blocks, including increased flexibility, reduced material and weight, and added surface area for moisture transfer during sweating.
These three components of the garments according to the invention are connected together by stitching at the edges of the garment. That is, the outer fabric, foam, and inner fabric are sewn together around the edges, and the foam is not in any way bonded to the shell or the liner by adhesive, or in any other manner, since such additional bonding may reduce the effectiveness of the garment for providing warmth or moisture permeability.
The garment system according to the present invention is eminently successful even in harsh windy environments. For instance even with a temperature in the range of -20.degree. to +10.degree. F., with the wind continuous at 20-30 miles per hour, one wearing the garment system according to the present invention can remain warm and comfortable. Protection is also provided under more moderate conditions, such as 10.degree. F. to 50.degree. F.
According to the present invention there also is provided a method of protecting a human against cold weather. The method according to the invention comprises the following steps Constructing an upper body garment for covering the human's upper body and arms, the upper body garment having arm portions, and the garment constructed by disposing a layer of open cell foam at least 1/2 inch thick between an interior lining fabric and an outer fabric having an air permeability of less than 10 cubic feet per minute per square foot at 0.5 inches head of water, and having a moisture vapor transmission at least 1,000 grams per square meter per 24 hours; by stitching around the edges of the garment to hold the foam, lining, and outer fabric together at the garment edges and elsewhere if required; constructing a lower body garment, having leg portions, in the same manner as the construction of the upper body garment; and, providing the human with the upper body garment and the lower body garment covering the human's body, arms, and legs, so that the upper body garment and lower body garment are the only cold weather garments protecting the human's body, arms, and legs, and so that the human has no garment on the body, arms, or legs that has poor moisture vapor transmission.
It is the primary object of the present invention to provide improved and effective cold weather garments, and a method of utilization thereof to protect a human from cold weather. This and other objects of the invention will become clear from an inspection of the detailed description of the invention, and from the appended claims.